Charge air coolers are used in conjunction with turbocharged internal combustion engine systems. In such systems, residual energy from the combustion exhaust is recaptured through an exhaust expansion turbine, and the recaptured energy is used to compress or “boost” the pressure of the incoming air (referred to as the “charge air”) being supplied to the engine. This raises the operating pressure of the engine, thereby increasing the thermal efficiency and providing greater fuel economy.
The compression of the charge air using the exhaust gases typically leads to a substantial increase in temperature of the air. Such a temperature increase can be undesirable for at least two reasons. First, the density of the air is inversely related to its temperature, so that the amount of air mass entering the combustion cylinders in each combustion cycle is lower when the air temperature is elevated, leading to reduced engine output. Second, the production of undesirable and/or harmful emissions, such as oxides of nitrogen, increases as the combustion temperature increases. The emissions levels for internal combustion engines is heavily regulated, often making it necessary to control the temperature of the air entering the combustion chambers to a temperature that is relatively close to the ambient air temperature. As a result, cooling of the charge air using charge air coolers has become commonplace for turbocharged engines.
In some applications, the charge air is cooled using a liquid coolant (for example, engine coolant). A charge air cooler that uses liquid coolant to cool the charge air can be mounted directly to the engine, and in some cases can be located directly within the air intake manifold of the engine. Such an arrangement can pose problems, however. In order to route the liquid coolant into and out of the charge air cooler, the flow of the charge air may be blocked in certain portions of the cooler. While attempts are made to minimize the impact of such blockages, they have been found to have substantial impact on the distribution of the air to each of the individual cylinders, causing inefficiencies in the operation of the engine. Thus, there is still room for improvement.